Methane Wash Column Buffering for Stable Cryogenic Gas Separation
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Solution Overview
Problem
The existing cryogenic distillation processes for separating methane, carbon dioxide, and hydrogen are limited in their ability to quickly adjust to changes in feed flow rates, leading to instability and safety hazards due to the reliance on liquid carbon monoxide storage, which is slow to respond to demand fluctuations and poses security risks.
Innovation Solution
Storing liquid methane downstream of the CO/CH4 column and upstream of the methane wash column, where it serves to purify hydrogen and provide refrigeration, allowing for the variation of the methane purge flow rate to match demand changes, thereby stabilizing the heat exchange line and reducing the need for carbon monoxide storage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If liquid carbon monoxide storage is used to improve feed flow adjustment, then the speed of change of feed flow increases, but safety hazards and instability increase due to security risks of large amounts of liquid storage
Solution Approach 1:
The invention extracts the storage function from liquid carbon monoxide and transfers it to liquid methane. By removing the harmful substance (large amounts of liquid CO) from the system while maintaining the buffering capability through liquid methane storage, the safety hazards are eliminated while preserving the ability to adjust feed flow rapidly.
Solution Approach 2:
Liquid methane serves as an intermediary substance that performs the storage and buffering function previously handled by liquid carbon monoxide. The liquid methane can be stored in larger quantities safely and vaporized to adjust feed flow rates, mediating between the need for rapid response and safety concerns.
2Manufacturing precision
If liquid methane amount is increased to improve purification capacity, then hydrogen purification improves, but the speed to build up liquid methane decreases when feed flow increases
Solution Approach 1:
The system maintains a pre-established liquid methane inventory in the cold box before feed flow increases occur. This preliminary storage of liquid methane ensures that when feed flow increases, the purification capacity is immediately available without needing to build up liquid methane from scratch, thus resolving the contradiction between purification capacity and build-up speed.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables faster and more stable adjustments to carbon monoxide and hydrogen feed flow rates, reducing the overall liquid carbon monoxide in the system, avoiding the instability and safety issues associated with carbon monoxide storage, and maintaining thermal equilibrium in the heat exchange line.
Implementation Method 1
provision of refrigeration by vaporization of the liquid methane purge in the heat exchange line
Implementation Method 2
separation by cryogenic distillation of a mixture of methane, carbon dioxide and hydrogen
Data Source
AI summary
In a process for the cryogenic separation of a feed mixture of at least carbon monoxide, hydrogen and methane, the feed mixture is separated in a methane wash column fed by a liquid methane stream at the top of the methane wash column to produce a gas enriched in hydrogen, a liquid stream from the bottom of the methane wash column is treated to produce a mixture of carbon monoxide and methane, the mixture of carbon monoxide and methane is separated in a separation column to produce a gas enriched in carbon monoxide and a liquid methane flow at least part of which forms a purge stream, the purge stream being varied to take account of load variations.